Many of those living with Alzheimer's are genetically predisposed to the condition, but one-third of cases can be attributed to risk factors like diabetes, obesity, smoking, and physical inactivity—the last of which is the most prevalent risk factor in the US, UK, and Europe. Why? Physical activity keeps blood flowing and boosts oxygen consumption, both of which help your brain function better, according to the Alzheimer's Association. Exercise also makes the brain work more efficiently, which helps to preserve the function that's left. And another benefit is a reduced risk of heart attack, stroke, and diabetes, each of which can contribute to Alzheimer's on its own. (Ease into excercise with Prevention's Fit in 10 DVD. You will see results in just 10 minutes a day.)

A recent study published in the Journal of the International Neuropsychological Society suggests exercise can build up a part of your brain that withers with Alzheimer's disease. Researchers at the University of Maryland School of Public Health put older adults on a moderate-intensity exercise program, and found that the thickness of the outer layer of the brain—called the cortex—increased, potentially offering protection against dementia.

So how much exercise do you need? In a study published last year in the Journal of Alzheimer's Research, researchers found that 150 minutes of moderate exercise per week—the CDC's recommendation for adults—can significantly improve memory performance after just 12 weeks.